• Type: Penicillinase-resistant penicillin
  • Dosage Forms: 250,500
  • Common Trade Names:

Adult Dosing

Skin infections, staphylococcal

  • 125-500mg PO q6h (1h before or 2h after meals)


  • 250-500mg PO q6h (1h before or 2h after meals)

Pediatric Dosing

Skin infections, staphylococcal

  • <40 kg: 12.5-25mg/kg/day PO divided q6h
  • >40kg: 125-500mg PO q6h


  • <40kg: 50-100mg/kg/day PO divided q6h
  • >40kg: 250-500mg PO q6h

Special Populations

  • Pregnancy risk: B (no evidence of risk)
  • Lactation: safety unknown
  • Renal Dosing
    • Adult: no adjustment
    • Pediatric: no adjustment
  • Hepatic Dosing
    • Adult: not defined
    • Pediatric: not defined


  • Allergy to class/drug
  • caution in asthma
  • caution in seizure disorder
  • caution in renal impairment

Adverse Reactions


  • anaphylaxis
  • serum sickness-like reaction
  • superinfection
  • C-diff
  • hemolytic anemia
  • leukopenia
  • agranulocytosis
  • neutropenia
  • thrombocytopenia
  • esophagitis
  • esophageal ulcer


  • nausea/vomiting
  • diarrhea
  • epigastric pain
  • urticaria
  • pruritus
  • fever
  • rash
  • eosinophilia
  • stomatitis
  • black hairy tongue
  • LFTs elevated


  • Half-life: 0.7h, if GFR < 10 then 1.8h
  • Metabolism: liver partially
  • Excretion: urine 50-70% (primarily unchanged), bile 10%
  • Mechanism of Action: inhibits cell wall mucopeptide synthesis

Antibiotic Sensitivities[1]

Group Organism Sensitivity
Gram Positive Strep. Group A, B, C, G S
Strep. Pneumoniae S
Viridans strep I
Strep. anginosus gp S
Enterococcus faecalis R
Enterococcus faecium R
Staph. Epidermidis S
C. jeikeium R
L. monocytogenes R
Gram Negatives N. gonorrhoeae R
N. meningitidis R
Moraxella catarrhalis R
H. influenzae R
E. coli R
Klebsiella sp R
E. coli/Klebsiella ESBL+ R
E coli/Klebsiella KPC+ R
Enterobacter sp, AmpC neg R
Enterobacter sp, AmpC pos R
Serratia sp R
Serratia marcescens X1
Salmonella sp R
Shigella sp R
Proteus mirabilis R
Proteus vulgaris R
Providencia sp. R
Morganella sp. R
Citrobacter freundii R
Citrobacter diversus R
Citrobacter sp. R
Aeromonas sp R
Acinetobacter sp. R
Pseudomonas aeruginosa R
Burkholderia cepacia R
Stenotrophomonas maltophilia R
Yersinia enterocolitica R
Francisella tularensis X1
Brucella sp. X1
Legionella sp. R
Pasteurella multocida R
Haemophilus ducreyi X1
Vibrio vulnificus X1
Misc Chlamydophila sp R
Mycoplasm pneumoniae R
Rickettsia sp X1
Mycobacterium avium X1
Anaerobes Actinomyces R
Bacteroides fragilis R
Prevotella melaninogenica R
Clostridium difficile X1
Clostridium (not difficile) X1
Fusobacterium necrophorum X1
Peptostreptococcus sp. S


  • S susceptible/sensitive (usually)
  • I intermediate (variably susceptible/resistant)
  • R resistant (or not effective clinically)
  • S+ synergistic with cell wall antibiotics
  • U sensitive for UTI only (non systemic infection)
  • X1 no data
  • X2 active in vitro, but not used clinically
  • X3 active in vitro, but not clinically effective for Group A strep pharyngitis or infections due to E. faecalis
  • X4 active in vitro, but not clinically effective for strep pneumonia

See Also


  1. Sanford Guide to Antimicrobial Therapy 2014